Aqualung is an advanced music player originally targeted at the
GNU/Linux operating system, today also running on FreeBSD and OpenBSD,
with native ports to Mac OS X and even Microsoft Windows. It plays
audio CDs, internet radio streams and podcasts as well as soundfiles
in just about any audio format and has the feature of inserting
no gaps between adjacent tracks.

Here's how the test looks like.

Pick a song that you know
really well, something that's in your bones like Siberian
Khatru. Grab it from CD using cdparanoia to have it as
a WAV file. Now open your favourite wave editor and slice the file
up into multiple consecutive sections. Be careful not to insert
silence, delete samples or alter any sample data. Save the slices to
separate files. Now convert the sample rate of some pieces to random
values (the example program shipped with the libsamplerate library will
let you do this in very good quality). Pick some pieces and convert
them to Ogg Vorbis
format. Pick some others and encode them to FLAC. Pick a few and convert
them to MONO. Now open up the Playlist editor of the music player in
question and add the files in order. Push play, and
listen.

Aqualung is a music player designed from the ground up to
provide continuous, absolutely transparent, gap-free playback across
a variety of input formats and a wide range of sample rates thereby
allowing for enjoying quality music: concert recordings and
"non-best-of" albums containing gapless transitions between some
tracks. (Multiple movements long compositions are often broken into
separate but gaplessly flowing tracks when mastered to CD.) Obvious
examples are The Song Remains The Same (Led Zeppelin), The
Dark Side Of The Moon (Pink Floyd), and Yessongs
(Yes). Besides the ability to play the music from these records
without a defect, Aqualung provides high quality sample rate
conversion, a feature that is essential when building large digital
music archives containing input sources conforming to various
standards. Aqualung passed our test – and it will pass yours,
too.

Features at a glance

On the input side:

Audio CDs can be played back and ripped to the Music Store with
on-the-fly conversion to WAV, FLAC, Ogg Vorbis or CBR/VBR MP3
(gapless via LAME). Seamless tagging of the created files is offered
as part of the process.

Internet radio stations streaming Ogg Vorbis or MP3 are supported.

Subscribing to RSS and Atom audio podcasts is supported. Aqualung can automatically
download and add new files to the Music Store. Optional limits for the age, size
and number of downloaded files can be set.

Almost all sample-based, uncompressed formats (e.g. WAV, AIFF,
AU etc.) are supported. For the full list of these formats, visit
the libsndfile
homepage.

On the output side:

Exporting files to external formats from Playlist and Music Store
is supported.

In between:

Continuous, gap-free playback of consecutive tracks. Your ears
get exactly what is in the files – no silence inserted in
between.

Ability to convert sample rates between the input file and the
output device, from downsampling by a factor of 12 to upsampling by
the same factor. The best converter provides a signal-to-noise ratio
of 97dB with -3dB passband extending from DC to 96% of the
theoretical best bandwidth for a given pair of input and output
sample rates.

LADSPA plugin support
– you can use any suitable LADSPA plugin to enhance the music
you are listening to. There are many different equalizer, spatial
enhancer, tube preamp simulator etc. plugins out there. If you don't
have any, grab these.

Other niceties:

Playlist tabs allow you to have multiple playlists for your music
at the same time, very similarly to multiple tabbed browsing in Firefox.

Track repeat, List repeat and Shuffle mode (besides normal
playback). In track repeat mode the looping range is adjustable (A-B
repeat). It is possible to set the looping boundaries via a single
keystroke while listening to the track.

Ability to display and edit Ogg Xiph comments, ID3v1, ID3v2 and
APE tags found in files that support them. When exporting tracks to
a different file format, metadata is preserved as much as
possible.

All windows are sizable. You can stretch the main window
horizontally for more accurate seeking.

You can control any running instance of the program remotely
from the command line (start, stop, pause etc.). Remote loading or
enqueueing soundfiles as well as complete playlists is also
supported.

State persistence via XML config files. Aqualung will come up in
the same state as it was when you closed it, including playback
modes, volume and balance settings, currently processing LADSPA
plugins, window sizes, positions and visibility, and other
miscellaneous options.

In addition to all this, Aqualung comes with a Music Store
that is an XML-based music database, capable of storing various
metadata about music on your computer (including, but not limited to,
the names of artists, and the titles of records and tracks). You can
(and should) organize your music into a tree of
Artists/Records/Tracks, thereby making life easier than with the
all-in-one Winamp/XMMS playlist. Importing file metadata (ID3v1, ID3v2
tags, Ogg Xiph comments, APE metadata) into the Music Store as well as
getting track names from a CDDB/FreeDB database is supported.

Aqualung is released under the GNU General Public License. For more
info, see the Misc page.